Debt (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Extinguishment of debt
Original principal amount	$ 894,507	$ 3,005,309	$ 1,468,708
Cash purchase price/repayment price	894,249	3,104,476	1,226,658
Gain (loss) on early extinguishment of debt, net	258	(201,486)	172,258
Senior Debt [Member]
Extinguishment of debt
Original principal amount	118,562	1,724,946	587,698
Cash purchase price/repayment price	120,935	1,874,829	545,618
Exchangeable senior notes [Member]
Extinguishment of debt
Original principal amount	180,259	1,145,642	653,993
Cash purchase price/repayment price	180,163	1,092,586	454,023
Secured mortgage debt [Member]
Extinguishment of debt
Original principal amount	595,656	134,721	227,017
Cash purchase price/repayment price	$ 593,151	$ 137,061	$ 227,017